Mitt Romney engaged in a last bout of campaigning in Youngstown, Ohio, on Monday. Ohio is widely considered Super Tuesday's biggest prize.

Michael Reynolds EPA /Landov

Super Tuesday 2012 is finally here, with Republican presidential preference contests — a mix of primaries and caucuses — occurring in 10 states from sea to shining sea.

While the 2012 race for the GOP nomination likely won't be over by Wednesday morning, it could seem far closer to being so, especially if Mitt Romney sweeps contests everywhere but, say, Georgia, where the former congressman from the Peach State, Newt Gingrich, is expected to have a good night.

Even if he doesn't take all of Tuesday's contests, it's still thought that Romney will add more of the 437 delegates up for grabs in the 10 states to his count than will his rivals, Rick Santorum, the latest not-Romney to give him a scare, Gingrich and Rep. Ron Paul.

In a race where the first candidate to reach 1,144 delegates wins the nomination, Romney starts the day with the wind at his back. His superior organization and money meant he got on the ballot pretty much everywhere. Only he and Paul are on the ballot in Virginia, for instance.

Meanwhile, the complicated delegate-allocation process means he can add to his overall total even in states he loses.

In any event, there will be a lot of moving parts on Super Tuesday. But here are some of the most important pieces to keep an eye on.

Ohio — All eyes will be on the Buckeye State (66 delegates), which is widely viewed as the grandest of all of Super Tuesday's prizes because of its symbolism. No Republican has ever made it to the White House without winning Ohio in a general election, and winning its primary will certainly boost the victor's argument that he can keep it out of President Obama's column in November.

The latest polls suggest Romney and Santorum are now tied in Ohio, with Santorum losing what once was a double-digit lead. The momentum there has clearly shifted to Romney.

That's bad news for Santorum, since he has staked his claim to the GOP nomination on his appeal to working-class voters in the industrial Midwest.

If Santorum wins, he lives to fight another day. If the former U.S. senator from neighboring Pennsylvania loses, he may fight on but likely in a cause that would seem increasingly doomed.

A Romney win in Ohio, after his narrow victory in Michigan last week, would increase the former Massachusetts governor's "inevitability" quotient.

The South — Newt Gingrich should easily win big in his native Georgia (76 delegates), which will likely be enough motivation to keep him slogging along for the foreseeable future. Not everyone buys into the concept that Georgia is so predictable. Middlebury College political scientist Matthew Dickinson thinks Georgia actually is a bigger deal than Ohio.

Still, if anyone not named Newt wins Georgia or even comes close, that would be perceived as the upset of the evening. But, again, the state is seen as Gingrich's to lose.

Which is why Tennessee (58 delegates) looms so large. Romney has yet to prove he can win in the South, the region that has been a Republican stronghold since the mid-1960s.

If Romney can win in Tennessee — and the latest polls show him essentially tied with Santorum there — that would give him the Southern street cred he has until now lacked. For this reason, Josh Putnam, the political scientist who runs the Frontloading HQ blog, calls Tennessee the "new hotness."

Delegates — The Republican race has become a delegate chase at this point, with all four remaining GOP candidates — and especially the Romney and Santorum campaigns — arguing in recent days that all that really matters is who is adding to their delegate totals.

Because of how delegates are awarded, Romney could lose the popular vote in Ohio and elsewhere and still capture enough delegates to significantly pad his totals.

Romney got an assist from Santorum and Gingrich, whose seat-of-the-pants organizations failed to qualify for the ballot in Virginia or in all of Ohio's congressional districts.

Romney has the most delegates at this point, though, amazingly, no one is certain exactly how many he has. By NPR's count, which includes only those delegates unequivocally committed to a candidate through the first ballot at the GOP convention, he has 118 delegates, while Gingrich has 29, Santorum has 17 and Paul 8. Some counts have Romney at 180. It's all because of uncertainties and disputes as to how delegates are being awarded. In a word, it's ridiculous.

While the exact number of delegates may be in dispute, the relative positions of the candidates based on rough numbers are clearer.

Romney has a commanding lead going into Super Tuesday. The question is, will anything that happens Tuesday change that? Right now, the smart money says that's unlikely.

Caucuses -- As Micah Cohen at the FiveThirtyEight blog reminds us, the caucus states of Alaska, Idaho and North Dakota shouldn't be discounted even though they haven't gotten the attention from the media or pollsters that the primary states have gotten. They have 87 delegates among them.

As Cohen writes:

"In 2008, Barack Obama's wins in the caucus states on Super Tuesday helped him to win more delegates from the evening, and turned what was initially perceived as a relatively poor performance for him into one that gave him some degree of momentum."

But again in the caucus states, Romney appears to be in solid position. Idaho, with its significant Mormon population, is part of the Mormon Corridor of the West, and Romney has done well in other states with large populations of his co-religionists, like Nevada and Arizona.

Meanwhile, while Romney won the Alaska caucus four years ago, that was before the Tea Party existed. And Paul, who has appeal to Tea Party voters, is the only GOP presidential candidate to make the physical trek to Alaska. So he conceivably could pull off a win there or in North Dakota.